Fuel injection Nozzle

ABSTRACT

A fuel injection nozzle has a valve member engageable with a seating to prevent fuel flow through an outlet orifice. The valve member is engaged by the narrower end of a stepped piston member the surface of which remote from the valve member is subjected to fuel under pressure to bias the valve member into engagement with the seating. A tubular valve element the interior of which is connected to a drain, is engageable with the surface but can be moved away from the surface to lower the pressure applied to the surface. The valve member lifts away from the seating when the pressure applied to the surface is reduced by fuel pressure acting on a further surface defined on the valve member. The valve element is connected to the armature of a solenoid.

This is a DIVISIONAL of application Ser. No. 08/318,090 pending filedOct. 5, 1994.

This invention relates to a fuel injection nozzle for supplying fuel toan internal combustion engine and comprising a nozzle body in which isdefined a blind bore, a seating defined adjacent the blind end of thebore, valve means movable axially within the bore, the valve means beingshaped for cooperation with the seating and being movable away from theseating to permit fuel to flow past the seating through an outletorifice and the valve means defining a surface against which fuel underpressure can act to lift the valve means from the seating.

Such nozzles are well known in the art and it is usual for the valvemeans to be biased into engagement with the seating by a strong springand for the surface defined by the valve means to have an area such thatthe force developed on the valve means when fuel under pressure issupplied to the nozzle is sufficient to move the valve means against theforce developed by the spring. The valve means therefore lifts from theseating when the fuel pressure attains a predetermined value andtherefore the timing of fuel delivery to the engine is dependent uponthe rise in the fuel pressure and the manufacturing tolerances of thenozzle.

In order to meet the operating requirements of modern engines it isnecessary for the timing of fuel delivery to the engine to be carefullycontrolled. This is the case particularly with compression ignitionengines and the object of the present invention is to provide a fuelinjection nozzle of the kind specified in which the initiation of fueldelivery is determined by a control signal which is supplied to thenozzle.

According to the invention in a fuel injection nozzle of the kindspecified the valve means defines a further surface against which fluidunder pressure can act to hold the valve means in engagement with theseating and there is provided a control element operable by a controlsignal from external of the nozzle, to reduce said fluid pressure whenit is required to lift the valve means from the seating.

According to a further feature of the invention said fluid underpressure is fuel which is derived from a fuel inlet of the nozzle.

According to a still further feature of the invention the fuel underpressure which acts on said further surface of the valve means issupplied from said inlet by way of a restrictor.

In the accompanying drawings:

FIG. 1 is a sectional side elevation of one example of a nozzle inaccordance with the invention,

FIG. 2 is a view similar to FIG. 1 taken at right angles to FIG. 1 withparts removed for the sake of clarity,

FIG. 3 is a view to an enlarged scale of a portion of the nozzle asshown in FIG. 1,

FIG. 4 is a section through a portion of the nozzle seen in FIG. 1,

FIG. 5 shows a modification to the nozzle seen in FIG. 1.

FIG. 6 shows in sectional side elevation an alternative construction fora part of the nozzle seen in FIG. 1; and

FIG. 7 is a section on the line 7--7 of FIG. 6.

Referring to FIGS. 1-4 of the drawings the nozzle comprises a nozzlebody 10 in which is defined a blind bore 11. Disposed at the blind endof the bore is a seating 12 and downstream of the seating there isformed an outlet orifice or orifices 13. Movable axially within the boreis a valve member 14 which is shaped for cooperation with the seating.The valve member is in general slightly smaller than the bore but it isprovided with a fluted portion 15 the flutes of which engage the wall ofthe bore to guide the movement of the valve member.

The nozzle body is provided with a flange which is engaged by a cap nut16 whereby the nozzle body can be secured to a nozzle holder 17.Interposed between the holder and the flanged end of the nozzle body isa pair of valve housings 18, 19 which are located in end to endrelationship. Moreover, the valve housings, the nozzle holder and thenozzle body are restrained against relative angular movement by means oflocation pins clearly seen in FIG. 1.

The nozzle holder defines a fuel inlet 20A which by way of a passagewhich extends through the holder and the valve housings, communicateswith the open end of the bore 11. Conveniently the valve housing 18defines recess in its face presented to the flanged end of the nozzlebody. The fuel inlet 20A in use, is connected to a source of fuel underpressure. Formed in the valve housing 18 as more clearly seen in FIG. 3,is a stepped bore 20 and slidable in the bore is a stepped piston member21. Intermediate the ends of the bore there is defined a gallery 22which as seen in FIG. 2, communicates by way of a passage formed in thevalve housings, with a drain passage 23 formed in the holder.

The narrower portion of the piston member 21 engages the valve member 14and extending inwardly from the end of the piston member which engagesthe valve member is a blind drilling 25 which communicates with thegallery 22.

The wider end of the piston member opens into a chamber 26 which isdefined by a recess in the valve housing 18 and this chambercommunicates with the fuel inlet 20A by way of a restrictor 27.

Slidably mounted in the valve housing 19 is a tubular valve element 28the bore in which communicates with the drain passage 23. The valveelement is movable by means of an actuator which includes an armature 29to which the valve element is connected and which is biased by means ofa spring 30 towards the valve body so that the valve element engageswith and can form a liquid seal with the wider end surface 21A of thepiston member 21.

Associated with the armature 29 is a solenoid which includes a coremember 31. As will be more clearly seen from FIG. 4 the core member iscomposed of two "E" cores with the pole pieces 32 defined by the centrallimbs, facing each other in spaced relationship and having curved polefaces which locate with clearance about the armature 29. The pole pieces32 are surrounded by electrical windings 33 which can be connected to asource of electric supply whereby when current is passed through thewindings the pole pieces will assume opposite magnetic polarity.

The armature is provided with a plurality of circumferential slots whichare evenly spaced along the length of the armature and the faces of thepole pieces are similarly slotted. When the windings are supplied withelectric current the ribs on the armature and on the pole faces tend tomove into alignment with each other so as to reduce the magneticreluctance of the magnetic circuit and it is intended that when thewindings 33 are energised the tubular valve element 28 should be liftedaway from the end of the piston member 21. It is therefore necessary toadjust the axial position of the core member 31 of the solenoid withinthe nozzle body and for this purpose the core member at its end adjacentthe valve housing 19, bears against a leaf spring 34 which is inengagement with the valve housing 19. The core member can be urgedagainst the action of the leaf spring 34 by means of an adjustableabutment 35 which is in screw thread engagement with a thread defined inthe passage 23. In addition, the spring 30 has a spring abutment 36which is in screw thread engagement with the abutment 35.

In the closed position of the nozzle the various parts of the nozzleassume the position shown in the drawings. The spring 30 acts tomaintain the valve member 14 in engagement with the seating 12 and theaxial position of the core member 31 is set so that when the windingsare energised the armature 29 will move against the action of the spring30 and in so doing will lift the tubular valve element away from thewider end of the piston member 21.

Assuming now that the inlet 20A is connected to a source of fuel underpressure and the windings 33 are not energised.

In this situation the force exerted on the end surface 21A of the pistonmember 21 due to the fuel pressure in the chamber 26 is greater than theforce exerted on the end surface of the valve member 14 which liesoutside the seating area and as a result the valve member is held by theforce exerted by the spring and by the difference in the forces due tofuel pressure, in engagement with the seating 12. When the windings 33are energised the armature lifts the tubular valve element 28 away fromthe piston member 21 and as a result the pressure in the chamber 26falls. The force exerted by the reduced fuel pressure acting on thepiston member is less than the force exerted on the valve member and asa result the valve member is lifted from the seating to permit fuel flowthrough the outlet orifice 13. Such movement moves the piston memberback towards the end of the valve element 28 so that the piston memberand valve member assume a position which is determined by the axialposition of the valve element and hence the armature. It is possibletherefore by varying the current in the armature to control the axialposition of the valve member 14 once it has opened so that the flow offuel through the outlet orifice 13 may be controlled.

When the windings are de-energised the valve element 28 moves intoengagement with the piston member 21 under the action of the spring 30and exerts a closing force on the valve member 14. The spring force issupplemented by the force generated on the piston member 21 by theincreased fuel pressure within the chamber 26.

The mass of the armature 29 is made as small as possible and the factthat the armature is of substantial length means that there is a largemagnetic path area for a given mass so as to achieve a fast response.

In the arrangement which is shown in FIG. 5, the armature is providedwith a helical groove or grooves as opposed to a plurality ofcircumferential and axially spaced grooves. The pole faces of the polepieces are similarly provided with helical grooves. Moreover, the coremember 31A is secured within the holder by encapsulation. In order toadjust the relative positions of the thread formations on the armatureand pole faces, the armature is angularly adjustable by means of a pin40 which is carried by a screw threaded adjustment member 41 located inthe outlet 23, the adjacent end of the armature being provided with aslot to receive the pin.

The valve member 14 and the piston member 21 can be formed as one piecewith the fluted portion 15 of the valve member deleted providing thevalve member can be passed through the narrower portion of the bore 20.In this case the piston member serves as a guide for the valve member.It would also be possible to construct the valve housing 18 as part ofthe nozzle body 10 if the valve member with or without the flutedportion 15, is of equal or smaller diameter than the narrower portion ofthe bore 20.

Turning now to FIGS. 6 and 7, there is shown an actuator which includesa hollow cylindrical armature 50 and a core member. On the outerperipheral surface of the armature is formed a helical groove orgrooves. The armature is located between the presented curved faces ofthe central pole pieces 51 of a pair of "E" cores 52 which form the coremember. As in the earlier examples windings 53 are wound about thecentral pole pieces and these are connected together so that whensupplied with electric current the central pole pieces 51 assumeopposite magnetic polarity. The "E" cores are encapsulated in a body 54and may be formed as solid material or by a series of laminations. Thepresented curved faces of the pole pieces 51 are formed with helicalgrooves which are complementary to the groove or grooves on thearmature.

As shown the core/body 54 is secured to a valve housing 55 by means ofbolts 56 which extend through elongated apertures in the body 54 andsandwiched between the heads of the bolts and shims 57 located next tothe body is a support plate 58 which carries a rotatable plug 59 whichextends with a small radial clearance, within the armature. The plug andarmature are formed from magnetisable material. In addition, the plugcarries a transverse pin 60 which is located within axial slots formedin the end of the armature.

In the example, the end of the armature 50 remote from the support plate58 is coupled to a valve member 61 slidable within a bore formed in thevalve housing 55. The valve member is shaped to co-operate with aseating defined in the bore and is biased by a spring 62 away from theseating to allow fluid flow between a pair of passages 63, 64 formed inthe valve housing thereby providing an ON/OFF valve function.Conveniently a plate 65 having a depending hollow spigot is incorporatedinto the body 54 and a further shim 66 is interposed between the springand the valve body.

When the windings are supplied with electric current the ribs definedbetween the grooves on the pole pieces and armature tend to move intoalignment and the initial adjustment of the angular position of thearmature is such that the armature moves downwardly against the actionof the spring 62 thereby moving the valve member into engagement withthe seating.

The plug 59 acts to convey the magnetic flux between the pole faces, anexample of a flux line being seen in FIG. 7, so that the armature canhave a thin wall section and therefore, be light. The travel of thearmature is set by the shims 57 and the spring force by the shim 66. Thearmature may be formed from the same material as the valve member but ifnot may be formed from for example, soft iron and attached to the valvemember. The plug 59 may be solid or formed as a stack or laminations.

The passages 63 and 64 may be connected to the chamber 26 and the drainpassage 23 of the fuel injection nozzles seen in FIGS. 1-5 so that theactuator may be used to control the operation of the fuel injectionnozzle. In this case however a separate spring corresponding to thespring 30 must be provided to bias the valve member 14 of the nozzle tothe closed position.

We claim:
 1. An actuator for a valve including a core member and anarmature, the core member comprising a pair of "E" cores having theircentral pole pieces presented to each other, the faces of said centralpole pieces being curved, said armature being of hollow cylindrical formand being located in spaced relationship between said faces, a helicalgroove formed on the outer periphery of the armature and complementaryhelical grooves formed on said faces of the pole pieces, electricalwindings carried by said central pole pieces and connected so that whenenergised the pole pieces assume opposite magnetic polarity, means foradjusting the relative angular position of the armature and the centralpole pieces and a plug located with clearance within the armature, theplug being formed from magnetizable material.
 2. An actuator accordingto claim 1, in which the cores are encapsulated in a body, said bodydefining elongated apertures whereby it can be secured to a support bybolts extending through said apertures, and a support plate retained bysaid bolts relative to the body said support plate mounting said plug.3. An actuator according to claim 2, including a pin carried by saidplug the ends of the pin being located in slots formed in the armatureto restrain the armature against angular movement.
 4. An actuatoraccording to claim 3, in which the plug is adjustably mounted on saidplate whereby the angular position of the armature relative to the polepieces can be adjusted.